Parse and Sequence complex, variable type, variable length keys into sortable
sequence of bytes.

examples/ directory contains sample inputs and reference outputs.
Refer to github.com/prataprc/golib/parsec instead of the local version
Append only store for persisting keys and values. Keys and Values can be saved
as []byte or string.
Some basic data-structure for BTree and a writeup to myself on how to go about
designing a file-format for saving BTree index in a file.
Cosmetic changes to ikey-testcase.